There isn't a built in way. That's not what Apple wants to happen so fuck the user I guess. Someone has written a script that monitors for if the lid is closed

There isn't a built in way. That's not what Apple wants to happen so fuck the user I guess. Someone has written a script that monitors for if the lid is closed and puts it to sleep. I haven't personally tried it though. https://github.com/pirj/noclamshell https://github.com/pirj/noclamshell